Nickel-Based Superalloys and Articles

Abstract

Rhenium-free nickel based alloys are provided. More particularly, the alloys comprise preferred levels and ratios of elements so as to achieve good high temperature strength of both gamma matrix phase and gamma prime precipitates, as well as good environmental resistance, without using rhenium. When cast and directionally solidified into single crystal form, the alloys exhibit oxidation resistance better than or comparable to rhenium-bearing single-crystal alloys, and creep rupture life comparable to rhenium-bearing single-crystal alloys. Further, the alloys can be processed by directional solidification into articles in single crystal form or columnar structure comprising fine dendrite arm spacing, e.g., less than 400 μm, if need be, so that further improvements in mechanical properties in the articles can be seen.

Description

BACKGROUND[0001]The present disclosure relates to nickel-based alloys, articles based thereupon, and methods of making the articles.[0002]Gas turbine engines operate in extreme environments, exposing the engine components, especially those in the turbine section, to high operating temperatures and stresses. In order for the turbine components to endure these conditions, they are necessarily manufactured from a material capable of withstanding these severe conditions. Superalloys have been used in these demanding applications because they maintain their strength at up to 90% of their melting temperature and have excellent environmental resistance. Nickel-based superalloys, in particular, have been used extensively throughout gas turbine engines, e.g., in turbine blade, nozzle, and shroud applications. However, designs for improved gas turbine engine performance require alloys with even higher temperature capability.[0003]Single crystal (SC) nickel based superalloys may be divided int...

AI Technical Summary

Benefits of technology

"The patent describes a new type of nickel-based superalloy that is rhenium-free and contains specific amounts of chromium, molybdenum, tungsten, aluminum, titanium, hafnium, carbon, and boron. The superalloy can be used to make articles with improved properties such as high strength and fatigue resistance. The method for manufacturing the article involves casting the superalloy and solidifying it into a single crystal or columnar structure with specific dendrite arm spacing. The resulting article has improved strength and fatigue resistance compared to other nickel-based superalloys."

Problems solved by technology

Gas turbine engines operate in extreme environments, exposing the engine components, especially those in the turbine section, to high operating temperatures and stresses.

To date, known superalloy compositions having lower Re content have not been able to provide the properties obtainable those having at least 3 wt %, i.e., the second generation superalloys.

And, because Re is so effective at strengthening Ni base superalloys, merely replacing Re with other elements typically does not provide alloys having the strength that can otherwise be provided by Re, or can degrade environmental resistance, such as oxidation and corrosion resistance.

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